1. Field
Example embodiments relate to photomasks. More particularly, example embodiments relate to extreme ultraviolet photomasks and methods and apparatuses for manufacturing the ultraviolet photomasks.
2. Description of the Related Art
Sizes of patterns formed on a semiconductor substrate may be reduced to satisfy a superior performance and a low price that users require. A wavelength of a light source used in a conventional lithography process may be reduced to meet such requirements. For example, a light of g-line (436 nm) band and of i-line (365 nm) band may be replaced with a light source of deep ultraviolet band or extreme ultraviolet band.
Since light of extreme ultraviolet band may be absorbed in a refractive optical material, extreme ultraviolet lithography may generally use a reflective optical system. Therefore, a path of a light incident on and reflected from a conventional extreme ultraviolet photomask may be non-perpendicular with respect to a top surface of the conventional extreme ultraviolet photomask. For example, a path of light incident on or reflected from the conventional extreme ultraviolet photomask light may be inclined at about 6 degrees with respect to a normal to the top surface of the photomask.
However, due to the inclined light path, a shadow may be formed due to a shading pattern (i.e., an absorbing pattern) on the photomask, i.e., a shadowing effect, thereby affecting progress of the light. The shadowing effect may cause deformation of a pattern being transferred to a wafer, e.g., degradation of a contrast characteristic and distortion of a critical dimension (CD) of the wafer pattern, and a problem of H-V bias.